As is known, wireless communications standards place stringent requirements on a wireless communication device's dynamic range of operation because the signal strength of received signals may vary by many orders of magnitude. To meet these requirements, wireless communication devices are designed using radio frequency (RF) integrated circuits (IC) that consume low power and produce little noise. As is also known, on-chip inductors are significant components of RF integrated circuits and are used in oscillators, impedance matching networks, emitter degeneration circuits, filters, and/or baluns. Thus, it is desirable to use on-chip inductors that consume as little power as possible and produce as little noise as possible.
As is further known, inductor performance is expressed as a quality factor (Q-factor), which is associated with the resonance of the inductor and describes both the ability of the inductor to produce a large output at the resonant frequency and the selectivity (i.e., the power ratio in decibels versus frequency) of the inductor. As such, the Q-factor is a key component in determining power dissipation and phase noise of integrated circuits. In general, inductors having a high Q-factor dissipate less power and thus improve the achievable gain. Further, high Q inductors allow an oscillating circuit to perform with minimal power injection from the driving transistor and hence minimize noise.
In addition, high Q inductors minimize the power leaking into adjacent channels that corrupts a receiver performance in nearby channels of communication chips, which degrade a receiver's sensitivity. Furthermore, higher dynamic range of wireless communication devices is obtained due to the intrinsic linearity of passive devices.
Not surprisingly, high Q inductors are a key element for RF integrated circuits to have low power consumption and to achieve the desired noise performance. While performance of wireless communication devices is a critical design issue it is typically balanced with manufacturing costs of the devices.
As is known, CMOS technology is widely used for cost effective fabrication of integrated circuits, including RF integrated circuits. However, on-chip inductors using CMOS technology are known to have a modest quality factor in the range of 5 to 10, which limit their usefulness is applications that require a high Q inductor, including some wireless communication applications.
Therefore, needs exist for a high quality factor on-chip inductor for use in many applications including wireless communication applications.